This invention relates in general to display systems and more specifically to binocular systems presenting different views from electronic image sources.
Head-mounted displays (HMDs) are useful for immersing a viewer in an artificial, or enhanced, visual world. Uses for HMDs include simulation systems, virtual reality applications, night vision, infravision, instrumentation displays and video games. In a binocular HMD separate views are presented to each of the user's left and right eyes. The use of separate views for each eye gives greater realism as the user is able to perceive stereo, or depth, effects.
It is common for the views to be generated by a computer using a digital imaging device such as a liquid crystal display. In such a system, each of the user's eyes is presented with a view from a separate image source. The presentation from the image source can be direct, reflected, partially reflected, or a combination of these. For example, where it is desired that the image source projection fill up the entire angle of view of an eye, the image source may be placed directly in front of the eye with interceding collimating lenses for proper focusing. A viewfinder, sightguide or other enclosure or housing is provided so that the user's field of view is restricted to viewing the image source alone. This can be done for both eyes.
Another possibility is to have an indirect view of the image source. This can be accomplished by using a half-silvered mirror which allows the image source to be placed at an off-angle from the user's line of sight. The user looks through the half-silvered mirror and is able to see through the mirror to a scene other than the scene presented by the image source. Meanwhile, the image source's projection is transferred via the mirror and, possibly, other optical devices, to the user's eyes so that the user sees the indirect image source projection superimposed on the other scene. For example, the view over which the image source projection is superimposed can be of the outside world, another image source-generated scene or scenes or information presented by other means.
However, a problem exists in that the trade-off between presenting an exclusive image to view to the user's eyes fully immerses the viewer in a simulated world, but prevents the user from seeing the real world. On the other hand, by using superimposed presentations, the degree of control over what the user sees is reduced. The superimposed images may overlap and conflict with each other. Also, it is difficult to build a device that provides a superimposed view to a user where the view or scene generated by the image source completely covers the user's field of view.
Although it is difficult to build large field of view devices that superimpose images, there are cases where such a superimposed image view is desirable. An example of this is in an aircraft simulator, or trainer, where the pilot needs to be presented with simulated views outside the cockpit while at the same interacting with a real-world physical instrument panel, controls and cockpit surrounding the pilot. Thus, it is desirable to create a head-mounted display that superimposes imaged views and alternative views, such as a direct view of an instrument panel, while minimizing the problems and shortcomings of such an approach.